On some wordpress version, we can not create new post because of error when update wordpress code. We can fix that by: 1. Go to https://build.trac.wordpress.org/browser/trunk/wp-includes/js/tinymce 2. Download wp-tinymce.js.gz and tinymce.min.js 3. Upload/replace these two files in your /wp-includes/js/tinymce folder 4. Empty your cache Maybe it will work for you !